A Seminar Report On
Engineering design thinking skills in the context of Electronic circuit design
By,
N.Soumya
154380003
Under the guidance of,
Prof. Sahana Murthy
IDP – ET
IIT-B
1
Table of contents
Chapter 1
1.1 Introduction
3
1.2 Literature review 3
1.2.1 Engineering design thinking 3
1.2.2 Learning Engineering design as thinking skill
1.2.3 Expert design process 6
1.3 Conclusion
7
Chapter 2
2.1 Own design analysis
8
2.1.1 Why this problem
8
2.1.2 How did I write the solution 8
2.1.3 Methodology 8
2.1.3.1 Content analysis
8
2.2 My design 9
2.3 Identification of design thinking skill and sub-skills
2.4 Analysis 15
5
13
Chapter 3
Expert design analysis
3.1 Methodology
16
3.1.1 What expert did 16
3.1.2 What I did
16
3.1.3 Did I interrupt 17
3.1.4 What were the questions asked in the interview
3.1.5 When did she keep quiet / when did she speak
3.1.6 Content of Interview 18
3.2 Analysis 21
3.3 Conclusion
22
17
17
Chapter 4
Summary of seminar
4.1 Additional design competencies 23
4.2 Competency to focus on 23
References
24
2
Chapter 1
1.1 Introduction
Engineering is an application oriented field. Engineering design is therefore an activity that most
Engineers participate in and are expected to excel at. However, it is also seen that Engineering design is
a skill acquired with practice. While the concepts and tools that will eventually aid the Engineer in
designing good quality systems, are taught explicitly, the design process is an unstructured entity.
People good at design, follow their own methods while approaching the design problem, which may
vary from designer to designer and domain to domain as well. Its importance combined with its
unstructured nature has prompted many researchers to delve deep into understanding Engineering
design process and Engineering design thinking. This included looking at expert design methods, and
expert-novice design differences to find the skills, and activities that go into a good design.
In my seminar, I approached engineering design thinking skill from multiple perspectives in the context
of electronic circuit design. The perspectives being:
• Analysis of literature – engineering design from engineering education research journals
• Analysis of own design process for detailed design of one problem related to electronic circuit
design
• Analysis of design process by a 2nd year PhD student (in electrical engineering).
From the three perspectives, I hope to answer the question on 'What is Engineering design thinking' in
the context of electronic circuit design.
1.2 Literature review
1.2.1 Engineering design thinking
Engineering design has been defined by Dym et al. [1] as, 'Engineering design is a systematic,
intelligent process in which designers generate, evaluate and specify concepts for devices, systems, or
processes whose form and function achieve clients' objectives or users' needs while satisfying a
specified set of constraints'.
They go on to list some abilities that taken together constitute the Engineering design thinking. The
abilities are:
• Design thinking as divergent – convergent questioning
• Thinking about system dynamics
• Reasoning about uncertainty
• Making estimates
• Conducting experiments and
• Making design decisions.
The authors explain that asking questions is the first step to design process. Systematic questioning that
includes low level (existential) as well as deep reasoning (phenomenon) questions, help shape the
design process. According to them, design thinking is a series of continuous transformations between
concept domain and knowledge domain which correspond to divergent thinking and convergent
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thinking respectively.
The ability to anticipate unintended consequences is the basis of thinking about system dynamics.
Foresight and the ability to reason combined with exposure to unintended consequences, help develop
this thinking process.
Engineering systems are often riddled with imperfect model, incomplete information and ambiguous
objectives. Dealing with such systems is what constitutes reasoning about uncertainties. This requires
the designer to have probabilistic reasoning ability. To a large extent, visual processing and pattern
recognition helps in this thinking process.
Presence of a number of variables with a variety of interactions causes the problem to become difficult
and beyond the ability of human beings to tackle them. Strategies such as selectively focusing on
important parameters and identifying ignorable parameters can reduce the variable and interaction
space, thereby making the problem a more solvable one. This calls for estimate making skills.
The authors also argue that making decision decisions is a rational process that it involves choosing
among alternative designs. A probabilistic model (Hazelrigg model) of design decision making would
take into account uncertainty, risk, information, preference, and external factors such as competition, to
arrive at an optimum decision. On the other hand, a deterministic model (Radford and Gero model)
recommends a goal oriented approach where decisions are made based on performance optimization.
Decision matrix may be used to evaluate between alternate design concepts.
In the meta-analysis paper by Mehalik et al. [2], the authors have broken down the design process into
multiple stages, many of which may run in parallel. The stages that they have defined include
• Exploring problem representation (involves framing of the design task)
• Exploring graphical representation / visualization (using visual means to look at overall
configuration)
• Using functional decomposition (breaking big problem into smaller interactive parts)
• Exploring engineering facts (helps in designing from first principles)
• Exploring issues of measurement (helps come up with proper tools for testing and evaluating
design)
• Building of normative model (helps look at ideal design outcome that are unencumbered by
constraints)
• Exploring scope of constraints (helps look at those constraints that limit the goals of a design
and evaluate in what ways the constraints are affecting the design)
• Redefining constraints (helps in assessing importance of constraints to the design problem)
• Conducting failure analysis (helps in looking at under-performances in the design
systematically and gain knowledge from it)
• Validating assumptions and constraints (helps meet expectations from design)
• Searching the space for design alternatives (helps evaluate solutions that meet the criteria)
• Examining existing designs (helps by providing basis to improve upon or provide ideas)
• Following iterative design methodology (recursive nature warranted due to outcomes of
interactions with other stakeholders)
• Exploring user perspectives (helps meet user requirements as well as gain from their
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•
experiences)
Encouraging reflection on design process (helps in restructuring and transforming experiential
knowledge)
In her PhD thesis entitled 'Development and assessment of engineering design competencies using a
technology enhanced learning environment', Mavinkurve [3] proposes a set of 5 competencies as the
most important skills in Engineering design thinking. The competencies are
• Structure open problem
• Information gathering
• Multiple representations
• Divergent thinking
• Convergent thinking
The author further elaborates each of the competencies to sub-competencies. A good design thinking
process would involve effective use of these competencies.
1.2.2 Learning Engineering design as thinking skill
One of the methods that Dym et al., [1] recommends so as to learn engineering design thinking as a
skill is the use of project based learning (PBL) model. This model is based on Kolb's model of
experiential learning. Some of the advantages of PBL are:
• Enable extension of learnt concepts to new contexts (Transfer)
• Improves retention
• Enhances design thinking
In order to be effective, PBL demands presence of certain skills. These include expertise in domain,
being able to communicate well and be able to work in a team. One example of PBL is the Capstone
experience. In this model, students work on real projects and in the process of project execution, learn
valuable skills including design skills.
Atman et al., [4] have discussed extensively about acquiring a language of design. They argue that as
students progress from freshmen to their senior years, their exposure to varying kinds of formal design
methodologies enable them to internalize design language. The language includes words and phrases
that are basic design strategy terms such as 'Brainstorming', 'Prototype / mock-up', 'Perform user
testing', 'Meet with client', 'Define specifications / requirements', 'Use design tools (RAM/Gantt,
decision/alternatives matrix'. The authors claim that by acquiring such design language, students
consciously apply them in their design process and therefore learn better design process. The authors
successfully verified their hypothesis on students who are enrolled in capstone courses that subscribe to
PBL. Their experiments also demonstrated that the information gathering in terms of importance given
to certain kinds of information by senior students, was similar to experts at theoretical level.
Dym et al., [1] have a different view of language of design. They go a step ahead from popular
perception that Mathematics is the language of engineering design, and believe that design language
includes drawing, sketching as well as other types of human cognition. They argue that to be effective
designers, one must have knowledge of design procedures as well as attributes of design object. They
state that the complete representation of design would include design intentions, plans and behaviour.
Accordingly they list a set representations that are useful in engineering design thinking. They are
• Verbal / Textual - Constraints, limitations, documentation etc.
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•
•
•
•
•
Graphical representation - Sketches, rendering, engineering drawing.
Shape grammers - Rules of syntax: combine simple to complex shapes.
Features - Aggregate geometric shapes.
Mathematical / analytical models – express function or behaviour of artefacts
Numbers - Value, dimension and so on.
1.2.3 Expert design process
Atman et al., [5] did an analysis of variation in engineering design process as seen in freshmen, senior
students and experts. To bring out the differences, they analyzed design process of the three categories
of people for a given engineering problem. The significant design activities that they focused on in this
study were
• Problem scoping and information gathering ( in terms of time spent, number and categories of
information requests)
• Project realization ( in terms of time in decision and time in project realization)
• Consideration of alternate solution (in terms of number of objects)
• Total design time and transitions (in terms of activity transitions and rate of activity transitions)
• Solution quality (in terms of number of constraints met and assessment by designated
evaluators)
Their findings indicate that experts spend maximum time on problem scoping and information
gathering, much more than either freshmen or seniors. They also spent more time on project realization
and actively considered alternate solutions. While freshmen and seniors mostly neglected alternate
solutions, seniors spent longer time in project realization. In terms of activity transitions, the behaviour
of seniors matched the expert behaviour. The solution quality of senior students also came closer to
expert design quality.
In another study by Cross, [6] strategies of three exceptional designers were observed and a common
underlying flow derived. This flow is depicted by the illustration 1. This image has been directly taken
from the paper [6].
Illustration 1: Strategies followed by expert designers. Image source: Cross.N [6]
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1.3 Conclusion
In the literature review, I explored different facets of engineering design thinking in terms of skills,
competencies, activities, strategies. I also read about teaching design thinking and role of design
language in design thinking ability. Finally I read about expert design strategies to get an overall view
of what design thinking is all about.
In the next section, I have analyzed my own design to see if the insights that I obtained from literature,
map to my own design thinking process in the context of electronic circuit design.
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Chapter 2
2.1 Own design analysis
In order to explore engineering design thinking skills, I took up a design problem in the field of analog
electronics. The topic chosen was the design of a public address system for convocation hall at IIT
Bombay. The public address system was supposed to cater to programs involving predominantly
speech input.
2.1.1 Why this problem
This problem of designing a public address system for a specific location was chosen because it is rich
in solution space. There are multiple ways of tackling the problem and hence it provides the designer
with a multitude of design possibilities to explore. Also, the solution borrows from a number of
concepts of electronic circuit design. Public address system design is a common design problem. Any
community based venue such as halls, transport terminals, hostels, hospitals, malls and so on, have a
public address system installed. Each solution is different due to many parameters such as number of
inputs / outputs, structure and space where the system is being installed, and the purpose for which the
system has been designed. To the best of my knowledge, there is no single source from where one can
readily pick up instructions and design the solution. There are a variety of disparate sets of information
available to the designer and the task is to sift through and identify relevant information and use it
effectively and come up with the solution. Having said that, there is nothing creative about the solution
and is at the innovation level.
2.1.2 How did I write the solution
In order to arrive at an approximately complete design, I referred to standard electronic design
reference books, catalogues and reference manuals from audio equipment solution providers like
Bosch, JBL, Audix systems and so on, datasheets of different amplifier IC's, online tutorials and
discussion forums.
2.1.3 Methodology
After writing the design solution, I went through the design and annotated sections in the design that
corresponded to a new activity in the design process. By doing so, the design could be easily
categorized as main design concept and detailing of the concept. The main design concept
corresponded to the activity. For instance, while designing the rectification stage of power supply, I
annotated one section as, 'Arrival of criteria for selection of rectifier diodes'. This was a main activity
while the detailing included the use of formula and substitution of values to arrive at specifications for
the rectifier diodes.
2.1.3.1 Content analysis
Content analysis involves firstly the decision on unit of analysis (Single word / sentence / paragraph /
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action). This is then followed by decision of codes (categories) to be applied to the units of analysis.
My unit of analysis was 'one design action'. The main design concept which that I had used as
annotations for my design, corresponded to 'one design action' and hence was used as the unit of
analysis. For the codes, I used Madhuri's categories of sub-competencies. This step enabled me to
identify which engineering skills and sub skills I used in my design process. Next, I mapped the unit of
analysis to the codes. This process is equivalent to applying theory to the categories in grounded theory
approach.
2.2 My design
Problem statement:
Design a public address system for convocation hall. Consider the purpose to be for talks and speeches.
Write your answer in as much detail as you can.
Action here: Defining the basic structure of the design
The basic blocks in my design will have
• Microphones at the input
• Mixer stage to combine microphone signals
• Voltage amplification
• Power amplification
• Loudspeakers
• Necessary Power supply
For a room of size of convocation hall, at least 16 speakers may be required. For speech, assume
normal speakers of about 15Watt power rating each. Then at the output of power amplifier, the power
must be P = 16 * 15 = 240 Watt. Perhaps 16 speakers of 15 Watt may be too less. Let me reconsider by
looking at available speakers and their specifications.
Action here: The assumption on number of speakers required is being made. Sound pressure levels can
also be used.
Suppose I use 40 Watt metal column speakers (LA1- UM20E – LA1-UM40E) Bosch column LS
model.
The specifications given are
High sensitivity
Excellent music and speech reproduction.
6 * 100V taps and 8 ohm settings
If I use 20 Loudspeakers of 20 Watt each, net power required = 400 Watt. The use of such smaller
loudspeakers but greater in number will aid in reducing reverberations.
Alternately, If I use 15 loudspeakers of 40 Watt each, then the net power required is 600 Watt. These
will be larger speakers and may not solve reverberation problems. Reverberation may need to be sorted
by location and placement only.
Note 1: Do not place speakers in direct line of pickup from microphone. Possible risks include howling
noise and burnout of coil of speaker and eventually speaker damage.
Note 2: Number of speakers decision can be based on required sound pressure level (SPL)
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Connecting all the loudspeakers to the power amplifier:
Action here: Method of connecting speakers using transformer (step down)
To connect the loudspeakers to the single output power amplifier, I need to use transformers.
When single power amplifier drives many loudspeakers, typically high voltage systems are used.
In a typical high voltage system, a transformer at output of power amplifier, steps up voltage to ~ 70V
or 100V at full power. Each speaker has a step down transformer that matches the 70V or 100V line to
speaker impedance.
Typical loudspeaker signal: High voltage (70V to 100V), low current (1.41A), high impedance (50
Ohm). Advantage of high voltage operation is • Lower power loss due to lower cable heating. This is because current values are low.
• It is easy to connect multiple speakers to single 8 ohm amplifier output.
High voltage power amplifier design:
Requirements:
• Power supply source
• Proper transformers
• Amplifying module
Action here: Transformer specifications for power supply is being derived here
Power supply: Build a bridge rectifier based power supply.
Power supply is required to drive speakers, amplifier circuit and also the microphones or other input
devices.
For power supply design, primary of transformer is connected to ac mains which is about 220V AC.
Let secondary of the transformer be 100V.
Assumption: considering Np = 500 turns.
We have the formula: Vs/Vp = Ns/Np
Thus, Ns = (500*100)/220 = 227.27 ~ 228 turns.
Thus the secondary of the transformer must have 228 turns.
Action here: Arrival of criteria for selection of rectifier diodes
In the bridge rectifier circuit, the peak rectifying diode voltage = 100V.
Assuming power output needed is 1000 Watt.
Then Power = Voltage * Current.
I = P/V = 1000/100 = 10 A.
Diodes should be chosen such that they have a current capacity of minimum 10 A and forward voltage
drop of 100 V and peak inverse voltage of 2*V = 200V.
Action here: Arrival of criteria for selection of filter capacitor
After rectification, filtering is required to remove ripples from the rectified voltage.
Peak voltage in RMS is = 100 V
Vpeak = √2 * Vrms = 141.42 V
Vdc = 2 Vpeak / π
10
Vdc = 90.031 V
Vripple = 141.42 – 90.031 = 51.389 V.
Vripple (peak to peak) = 102.778V
Required ripple voltage is = 5% of peak to peak = 5.1389 V
Thus the capacitance = (T * Vpeak) / (Projected load * required ripple voltage)
T = 1/f where f is the mains frequency = 50 Hz.
Thus T = 0.02 seconds.
Projected load can be assumed to be the power amplifier load which is say 8 ohm.
Thus capacitance = (0.02 * 141.42)/(8 * 5.1389) ~ 6879 μF.
For power amplifier, use MOSFET based amplifier circuit.
Mixer module:
Action here: Criteria for voltage amplifier for microphones
Now to focus on the input sources. To combine multiple inputs, mixer circuit is necessary.
For this design, microphone inputs and line inputs are considered. Line inputs can include drives, CD
player and so on.
Expected microphone output voltage = 2mV RMS
Expected line input voltage = 200 mV RMS.
To bring voltage levels of microphones and line devices to the same level, the microphone inputs
require a voltage amplification of about 100 which translates to about 40 dB.
If we use operational amplifiers connected in inverting mode, the required voltage amplification can be
obtained. Since the frequency range is in the audio frequency range, a high input impedance general
purpose operational amplifier can be used for this purpose.
Thus for an inverting amplifier configuration, gain can be represented as:
Gain = (-Rf)/Ri
Since a gain of 100 is required, Rf of 100 Kohm and Ri of 1 Kohm should serve the purpose. Too high
resistance value at the feedback may cause excessive bias currents to flow and loading of the
microphones.
Use an input capacitor of 10 μF to block dc signals.
Line inputs do not need this voltage amplification stage. They can be directly connected to the
summing amplifier stage.
Action here: Design of the summing amplifier
The purpose of the summing amplifier stage is to combine all the input signals and get a single output.
The summing amplifier can be built with a nominal gain of about 2. Thus a series resistance of
47Kohm and a feedback resistance of about 100 Kohm is used.
Thus at the output of the summing stage, the voltage level is about 400 mV RMS.
Power amplification stages:
Action here: Arriving at criteria for audio amplifier
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To add driving power to this signal, it needs to be amplified to 1000 Watt with 8 ohm load (Assumed
criteria)
Thus Voltage input required at power amplifier input is:
P = V*V / R
Thus V = √ (P * R) = √ (1000 * 8) = 89.442 V.
Thus voltage amplification required = 89.442 V / 400 mV = 223.
Thus minimum gain required is 223.
Action here: These are some design feasibility thoughts
To get that degree of gain in one stage is not realistic. This may also affect the bandwidth since they
have an inverse proportionality. So build a smaller gain voltage amplifier followed by a small power
booster stage using a class AB push-pull configuration.
The output of this can be connected to an audio step up transformer which will boost the audio signal
voltage to required level for the next stage of power amplification.
Action here: Design process of audio voltage amplifier
At this point the signal strength is = 400 mV RMS.
There is a need to increase voltage. The peak voltage is
Vp = 400 mV * 0.707 = 282.8 mV.
A gain stage of 15 will raise this voltage to ~ 4.242 V which is acceptable.
Let us consider a non-inverting amplifier. This configuration has a high input impedance and so low
loading on the previous stage. The gain is given by
Gain = 1 + (Rf/Ri)
Let the supply be +15V.
If Ri is chosen as 1 Kohm, gain as 15 then, Rf = 14 Kohm.
Any general purpose audio range op-amp should suffice as the audio frequency range of 20Hz to
20KHz is nominal for most opamps with such gain.
Note: Look for amplifiers with at least 1MHz gain bandwidth such as MC33182, LM833 etc.
At peak of say 400mV * 15 = 6Vp and 12Vp-p, current at load of 1 Kohm is (12V / 1Kohm) = 12 mA.
Current in the feedback network = (12)/(14+1) = 0.923mA.
Thus 12 + 0.923mA = 12.923 mA is the current requirement.
This is well under the limit of 20mA output current limit for general purpose opamps.
Action here: Design of a power amplifier stage to enable to drive a transformer at output
Now, to increase the current drive using a single stage class AB push pull amplifier so that it can drive
the step up transformer.
Consider the bias current Ibias = (V – 1.4V)/2*R = 6.8/R considering V = 15V.
If load resistance Rl = 10 ohm, I saturation = Vceq / Rl = 12V/10 ohm = 1.2A.
I average = Isat / π = 0.382A
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If Ibias = 1.7mA, then the drain current is = Idc = 1.7mA + 0.382A = 0.3837 A.
Maximum ac output power = (15*15)/(8*10 ohm) = 2.8125 Watt
Construction of audio transformer:
Action here: Designing the audio step up transformer to isolate sections with different power levels as
well as step up the voltage.
Once again here, Vp/Vs = Np/Ns
Considering Vp = 12 V, Vs = 100 V, Np = 10, Ns =83.33 ~ 84 turns
Thus, Ip/Is = Ns/Np
We have Ip = 383mA, Ns = 84 and Np = 10, Is = 45.59mA.
Thus at the secondary of audio transformer, with Ns:Np = 84:10, voltage V = 100 V, I = 45.59mA.
This is the specification for the input of the power amplifier stage.
A MOSFET based push – pull circuit can be built to provide an output of nearly 1000 watts. The design
procedure for this is not clearly given in the documents reviewed by me.
2.3 Identification of design thinking skill and sub-skills
To identify skills and sub-skills, I used Madhuri's compilation of design competencies summarized in
table 1.
Design Competency
Sub-Competency
Structure open problem (SOP)
SOP1: Identify specifications from given open
ended problem
SOP2: Decide structure based on specifications
SOP3: Implement design steps sequentially
SOP4: Write problem statement in structured
manner
Information gathering (IG)
IG1: Decide all relevant sources of information
IG2: Use sources to extract relevant information
Multiple representation (MR)
MR1: Construct valid representation for given
design problem
MR2: Justify consistency between different
representations required in design problems
MR3: Apply representations to solve design
problem
Divergent thinking (DT)
DT1: Write multiple solution ideas for given
problem
DT2: Suggest multiple solutions based on
specifications/ constraints
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DT3: Analyze multiple solutions based on pros
and
cons
DT4: Analyze solutions using different problem
solving methods
Convergent thinking (CT)
CT1: Select appropriate solution based on proscons analysis
CT2: Select solution based on principles
CT3: Justify chosen solution
CT4: Evaluate solution based on constraints
CT5: Write assumptions for solving the problems
CT6: Justify assumptions
CT7: Write complete solution using appropriate
mathematical formula
Table 1: Compilation of competencies and sub-competencies proposed by Madhuri [3].
Next, I did a mapping of the sub-competencies from Madhuri's table to each unit of analysis derived
from my design. The mapping is summarized in table 2.
Design Action
Competency and Sub-competency used
Defining the basic structure of the design
SOP2
The assumption on number of speakers required is SOP1, IG2, DT2, DT3, CT1, CT5
being made. Sound pressure levels can also be
used
Method of connecting speakers using transformer IG1, CT3
(step down)
Transformer specifications for power supply is SOP3, CT5, CT7
being derived here
Arrival of criteria for selection of rectifier diodes
CT2, CT3, CT7
Arrival of criteria for selection of filter capacitor
CT2, CT3, CT7
Criteria for voltage amplifier for microphones
SOP2, SOP3, IG2, CT4, CT5, CT7
Design of the summing amplifier
CT3
Arriving at criteria for audio amplifier
CT5, CT7
These are some design feasibility thoughts
SOP2
Design process of audio voltage amplifier
CT4, CT5, CT7
Design of a power amplifier stage to enable to
drive a transformer at output
CT4, CT5, CT7
Designing the audio step up transformer to isolate CT4, CT5, CT7
sections with different power levels as well as
step up the voltage
Table 2: Mapping of own design to competencies and sub-competencies
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2.4 Analysis
After mapping, I found that there were some sub-competencies which could not be explicitly mapped
or were not applicable at all. Some of the competencies and sub-competencies that were not mapped
were:
• SOP4: Write problem statement in structured manner
• MR1: Construct valid representation for given design problem
• MR2: Justify consistency between different representations required in design problems
• MR3: Apply representations to solve design problem
• DT1: Write multiple solution ideas for given problem
• DT4: Analyze solutions using different problem solving methods
• CT6: Justify assumptions
After reading the design question, a structure was decided based on the specifications (Convocation
hall and intended for speech). Subsequent to this step, I could have re-written the problem statement in
terms of the specifications mapped to actual components (Number of input sources, outputs, wattage
requirement and power supply capacity). This would have required the sub-competency of SOP4 which
is writing problem statement in structured manner. That would have made the design more systematic.
While none of the Multiple representation sub-competencies were explicitly used, they were implicitly
used. Electronic circuit design comprises of representing the design as blocks, schematics, equations
and mathematical calculations. Hence the multiple representations are implicit.
Though some amount of divergent thinking was done in exploring alternate circuit blocks for each of
the major blocks used in the design, they were not explicitly elaborated upon to a completion. Also
analyzing solution using different problem solving methods was not used at all in this design. I am not
sure of the requirement of this sub-competency. I presume it must be for validation of the design
decision. This sub-competencies therefore, did not fit my design process.
Finally in convergent thinking, though assumptions were made and acted upon, they were not justified.
Justification would have made the design more thorough and would have validated the current design.
Based on the mapping, about 65% of the recommended mapping was successfully done. There are
several gray areas in the design. The quality of the design can be improved in many ways and in doing
so the mapping may reach 100%.
Currently, the mapping has been only one way i.e. fitting codes to the design. However, the other way
mapping where codes are defined to convey the essence of the action, has not been done. This activity
might bring out new codes, not currently defined in Madhuri's competencies and sub-competencies.
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Chapter 3
Expert design analysis
3.1 Methodology
For the expert design analysis, a second year PhD student with a background in Electrical
engineering, was invited to solve a design problem.
The design problem was: Design a public address system for convocation hall. Consider the purpose to
be for talks and speeches. Write your answer in as much detail as you can.
The time allotted for the process was 1 hour for designing and half an hour for interview.
The designer was free to refer to books, internet for gathering information. The activities of the
designer on the computer pertaining to the kind of search queries and documents referred to were
recorded by a screen capture software – Cam studio.
An audio recorder was kept on to record any loud thoughts uttered by the designer. The whole design
activity was observed and recorded with time-stamp by two researchers (Aditi and myself).
3.1.1 What expert did
The expert first read the problem statement. After that she browsed through internet to get an idea of
the problem domain and a feel of the problem by searching up similar designs. In this context, she
looked up about public address system and existing public address systems specifically for
amphitheater since it comes closest to a convocation hall. From the search results, she got a broad view
(Wikipedia pages) and more detailed view (Maintenance handbook on public address system).
She then went on to look up flaws in public address system. This search enabled her to get a totally
different viewpoint on public address system which was about safety aspects. She then proceeded to
explore it in detail. This search also enabled her to view common pit-falls (Screeching sounds, power
back up) and look at solutions for some of them (Equalizers).
Parallely, she looked up existing public address schematic. This motivated her to look at different input
sources (Microphones, drives etc) and different types of loudspeakers and devote some thought towards
cost optimization while selecting them. She also came up with number of and specification of power
amplifiers required. In addition, she also arrived at the blocks that she would need in her public address
system (Microphones, signal processing units, amplifiers). Throughout the hour, the designer went back
and forth among the different documents, which she had opened as multiple tabs in the browser. At the
end of one hour, the designer was asked a number of questions related to her design process and she
answered them to bring out the details of her thought process during the design process.
3.1.2 What I did
I along with another researcher (Aditi) were passive observers of the whole design process. We
recorded with time stamp, activities of the designer. The activities included typing of queries, writing
on a paper or gesturing with hand or looking into space presumably reflecting on some information. At
the end of one hour, Aditi asked a few questions to the designer to elicit her thought process while I
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took notes during the interview.
3.1.3 Did I interrupt
The first one hour of the design time was allotted to the designer free of interruptions from the
observers. Interaction was restricted to sorting of some logistics issues related to browser and otherwise
no interruptions were made. This was to ensure the designer freedom to think without any bias.
3.1.4 What were the questions asked in the interview
While the first question was an independent one, the succeeding questions were asked in response to
statements from the designer or based on sentences written by the designer. The questions were asked
in simple language and contained sentences in English and Hindi. The switch to Hindi mixed with
English was made after it was observed that the designer used mixed language to express her thought
process. The questions I have listed below, therefore, has both English as well as Hindi words. The
Hindi words have been written as is without translating it to its English meaning.
The questions were as follows.
1. What was the first thing you thought after reading the problem?
2. So tum soch rahi thi to sabse pehle tum ne kaha ki space evaluation important hai. To yeh baat
how did it come into your head? Space evaluation as in what?
3. Aur phir ye sochne ke baad sabse pehle search kya kiya?
4. So yeh jo um whatever you have written over here - microphone amplifier this is …. (about
routers)
5. So the rest of this list you wrote from your mind or you saw it on screen / internet.
6. So you um first you thought of space then you wrote down the things which you think should
be there in a public address system. Then you added the things which you think are there in
public address system and then you are trying to find out that what are the typical flaws in um
public address system so that you can design for that for better system. Now you identified the
typical things which are needed which is the fire alarm in the public address system. So you are
trying to incorporate that in to in an automatic way in the public address system.
7. So now um you selected all the information regarding what is being um in a public address
system. So do you have some image in your head regarding what the public address system
is .... block diagram or something like that?
8. So you also mentioned something about the equalizer. Equalizer was not written anywhere - in
this diagram where equalizer.
9. Now going back to the first thing ok .maybe I am asking again.. so the first image that came
into your mind when you thought - what are the first question or first image that came into your
head when you read this question?
10. So when you were thinking of acoustic which acoustics are you thinking of matlab which...
11. Which room were you thinking of ?
3.1.5 When did she keep quiet / when did she speak
The designer kept quiet during the first one hour when she browsed through the internet to gather
information and design her system. The next half hour was devoted to question – answers where she
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responded to questions and explained her reasoning behind search queries, design decisions and so on.
3.1.6 Content of Interview
Aditi: What was the first thing you thought after reading the problem?
Richa: Space evaluation. Space is important - closed space open space
depending on that we will be looking at different types of techniques that is what I thought at first.
one imp pt that came into my head was for closed space according to me - fire alarms, voice alerts they
are probably always required.
mein uski taraf bhi dhyan de rahi thi - automatic hona chaiye ki manual hona chaiye - dono kaise
situation me tarike se bhi soch rahi thi.
Thik hai fire alarm manual and automatic dono hone chahiye.
Maine usko bhi ek do jagah kholke dekha tha automatic par woh - main concern mera aise hi tha ki
safety hona chahiye is ke according ... hona kya chahiye public address system me maine yeh dekha.
Phir fire alarm me dekha - fire alarm me automatic and manual both are required aur basically fire
alarm me its through words - not by sound or any other kind of beeps. Uska me dekh rahi thi. Matlab it
was written here ki mujhe uska dekhna hai.
and jis me paging system bhi hai. It should be for closed system umm umm paging open me phir bhi
use ho sakta hai par closed system me bhi hai. Um then intensity and sensitivity also have a role to
play.... point. That is also very much required . aap jab equalizer use kar rahe ho to screeching sound
mic so much of depends upon the intensity and sensitivity of sound. And then aur for voice alert and
all you need some battery backups - battery backups are also required. Maine uska bhi likha tha yahan
pe ki what is required. Then while writing monitored sources are what. Monitored sources like fire um
fire mic um it means... the non monitored sources recession ke liye they all need to be - is hisab se
dekh rahi thi.
and backup is also required - suppose aapke number of microphone and loudspeakers are connected
agar yeh line faulty tha then they can be transferred to the working line.
so that is also my - I was thinking in my design.
then what kind of speakers are required - there are a number of speakers. I decided column speakers
will be more good because of ..... optimization kaise hoga.
Aditi: So tum soch rahi thi to sabse pehle tum ne kaha ki space evaluation important hai. To yeh baat
how did it come into your head? Space evaluation as in what?
Richa: Abhi jaise public address system bolte hai na kuch to mere dimag me aaya ki kitni door tak
aawaz aana chahiye. toh ye to thik hai aap ne convocation hall ke liye bola tha par mein general se
narrow karne ki kosish kar rahi thi - bahot zyada bheed bi hote hai. then kitna intensity chahiye, kitna
coverage chahiye thik hai abhi umm convocation hall ka - hai - jo convocation hall me music system
use ho raha hai woh kisi aur program me use nahi kar sakte. to that way kitna - kitna coverage - pura
peeche tak awaz aana chahiye. ek ek baar aawaz peeche tak nahi aati hai. to kitna chahiye us hisab se
space is important.
Aditi: Aur phir ye sochne ke baad sabse pehle search kya kiya?
Richa: Sabse pehle search maine umm public address system - sabse pehle - existing public address
system kya hai matlab. uske baad maine search kiya tha flaws in public address system. Flaws mere
dimag me tha ki dekhna chahiye ki fire alarm kitna use hota hai. Yeh mujhe nahi pata. fire alarm me bhi
matlab um manual or phir um automatic woh kya kya hota hai - lekin mujhe - dimag me woh uphaar ka
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case yaad aaya tha. Mein aisa kuch hona chahiye. automatic hona chahiye aur phir manual hona
chahiye. so that way I was thinking ki mein phir correlate kar rahi thi ki - toh hamare convocation me
kya use hota hai - convocation ki usually but mujhe yeh kuch khaas mila nahi kuch amphitheatre me
alag kya hota hai - kya kya problems aa sakte hai. Convocation tak mein pahunch nahi payi. Generally
mein jitna loop holes soch pa rahi thi ki kya kya problems aa sakti hai. Third point was fire alarms to
hogi - pehle maine space phir large closed space maine dekha ki exisiting ka kaisa hota hai. Sirf flaw
bolte hi mere dimag me aaya ki without searching ki fire alarm is important - automatic ki manual ki
both. phir maine baad me yeh bhi dekha ki spoken words are heard more properly found in beaches zyada chaos create karte hai. words or - voice or automatic is more useful fire alarm - and paging
system - paging system is like you know how um directly you can come on the line or something it was
written - toh they will be more useful when u have a huge gathering - bahut bada open space hai but in
certain situation where things may go out of control or you know um paging is required in closed area
also where someone can come and you know um take over and guide the audience - this should also be
a possibility.
then mein actually parallelly soch rahi thi technical part also and things which were going in my head.
Activity and sensitivity - um because of - you use signal processors, amplifiers and then there is
something called - mixers are there and then something called equalizers are there so woh ek --- toh
maine pada hai --- ki whenever there are any kind of a conference toh woh log jab ---ya phir --- they
increase to certain decibels ki jab awaz karne lagta hai to they again lower the gain. thats all what I can
think.
Aditi: So yeh jo um whatever you have written over here - microphone amplifier this is (points to
design sheet)
Richa: Routers are not required - in convocation hall routers are not required. routers are required like
hostels me use karte hai. alag alag wings hai - toh routers like woh IP or internet connection you know
every thing can be transmitted. but according to me routers are not required in one hall where you have
stage and seating arrangement - they are more of a - so isliye maine routers ko drop kar diya.
Aditi: So the rest of this list you wrote from your mind or you saw it on screen / internet.
Richa: This thing I explored in my head but mixers is what I got from here and routers is again what I
have got from here but I crossed it out.
Routers are not required for here.
Aditi: So you um first you thought of space then you wrote down the things which you think should be
there in a public address system. then you added the things which you think are there in public address
system and then you are trying to find out that what are the typical flaws in um public address system
so that you can design for that for better system. Now you identified the typical things which are
needed which is the fire alarm in the public address system. So you are trying to incorporate that in to
in an automatic way in the public address system.
Richa: Nahi fire alarm automatic and manual dono hona chahiye. It is an electronic system maybe
something automatic may not work so manual also there must be a backing system because these
systems required with backup. Toh yeh manual bhi hona chahiye in case. People are not able to hear
once or twice. Kaise timing hota hai timer system woh sab manual hona chahiye.
Aditi: So now um you selected all the information regarding what is being um in a public address
system. So do you have some image in your head regarding what the public address system is .... block
diagram or something like that
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Richa: Ummmm microphone ummm and then ...... amplifier and then loud speaker and ummm over
here there will be feedback system also to reduce unwanted frequency .....that is all. Mein yahan tak
pahunch nahi payi. Padke laga ki it is required to remove out unwanted frequencies whatever is
coming.
Amplification is certainly required then what kind of mic is required - like fire mic is there, mic is there
...all the voices .... it should be decided what is req when sound is to be amplified whatever mic you are
using - goes to loudspeaker depending on what kind of a quality loudspeaker is required. Kuch unhone
diya tha Certain protocol diya tha BS5839 iske hisab se .... protocol was there depending on this
whatever output is required ummm usually more number of power amplifiers.
Aditi: This is in a ?
Richa: ummm actually jab mein dekh rahi thi usme toh baraf bhi use kiya tha - depends on power
requirement - output requirement
Aditi: So you also mentioned something about the equalizer. Equalizer was not written anywhere - in
this diagram where equalizer (Points to design sheet)
Richa: Equalizer here only ..... umm equalizer jaise maine bataya na woh um screeching sound - toh it
can be eliminated by this equalizer that is what I think..... Mixer .... screeching noise unwanted
noise ....they are removed by equalizer
Aditi: Now going back to the first thing ok .maybe I am asking again.. so the first image that came into
your mind when you thought - what are the first question or first image that came into your head when
you read this question?
Richa: I have to design a schematic for it and I have to ummm ..... see this is there na.. so um is ka
kuch technicality hoga us direction me dekha hai , iska usefulness kaise bhadana chahiye mujhe woh
dekhna hai. I had two pictures - technicality mein to cost optimization pecheck karna hai --- karna hai
umm fire alarm incorporate kar sakte hai kya - uske kya kya requirement hai toh woh dekhna hai - aur
kitna smooth you know the acoustic and asthetically - woh bhi involved hota hai - woh kaise usko
better kar sakte hai public address system mein. Convocation dekhange toh usme kuch matlab kya kar
sakte hai ki usko better karne ke liye aur -- toh dono tarah se soch rahi thi. Ye do sabse pehle mere
dimag me picture aaya tha. Technical point of view and then how to make it more smooth acoustic technically.
Aditi: So when you were thinking of acoustic which acoustics are you thinking of matlab which
Richa: Aawaz peeche clear nahi aati hai
Aditi: which room were you thinking of
Richa: Convocation. This convocation me peeche aawaz nahi aati hai . toh bar bar kisi ko bolna padta
hai aawaz dheemi aa rahi hai.
Already been tested according to audience toh aur woh abhi bhi kitne dino beech me cover karke baad
me bhi mere liye woh uphaar wala incident .... fire alarm to hona chahiye.
Soumya: In your block diagram you have um this mixer and equalizer together
Richa: I think so - because all the inputs will get mixed at that point and here is added up and then
equalizer will decide what to choose and what not to choose.....for further amplification.
Soumya: Do you think there should be some level of amplification before this or amplification should
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be only after this
Richa: After this. definitely
Soumya: And the feedback which you mentioned, um do you think it should be taken from after the
amplifier or before amplifier
Richa: After amplification.
Soumya: After amplification the feedback - do you think it will contain some
Richa: Maybe I am not sure
Soumya: In this amplifier, do you think we should have multiple parallel blocks or multiple sequential
blocks
Richa: Parallel blocks
Soumya: Parallel blocks meaning you will have different amplifier to different frequency ranges?
Richa: Ya. Parallel only is required.
Soumya: This whole block then you will break it into parallel blocks and then again mix it and give it
to loud speaker
Richa: No no individual speakers will be alloted for fire mic , cd player , mic from the stage .....
3.2 Analysis
The design written down by the expert and the interview transcript were the raw data to be used for
content analysis in this exercise. However, even before deciding on the unit of analysis, it was observed
that due to paucity of time, the design was still in the information gathering stage and the design
process had not proceeded to even structuring the problem. It was felt that at this design level, it would
not be possible to apply Madhuri's [3] codes of competencies and sub-competencies for analysis. The
examining of the design process from the competencies point of view may not yield any meaningful
insights into the thought process of the expert designer in this case. Therefore, other methods that are
used to analyze expert design process were explored. In this respect, research paper by Atman[5] and
also from Cross[7] provided different ways of evaluating expert design process.
Expert designers design process is evaluated based on five major factors, as per Atman et al. [5]
They are:
• Problem scoping and information gathering
• Project realization
• Consideration of alternate solution
• Total design time and transitions
• Solution quality
In the expert interview process that I undertook, the time allotted for the design process was too short
to complete the entire design. I realized this after the whole activity was completed. The designer could
therefore complete only the problem scoping and information gathering part of the whole design
process.
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However, Cross et al [7] suggest certain common stages in expert design process that is common across
domains. They observe that 'a systemic approach to the problem', 'framing the problem in distinctive
way' and 'designing from first principles', are some of the core ingredients seen in expert design
process. Specifically in one particular expert's instance, they code the expert's actions as – Rapidly
gaining experience, drawing inputs from personal problems/ views and adding unique idea to
contribute to innovativeness of the design. Seen in this context, the expert designer in my design
activity, followed all of them.
• Rapidly gaining experience: Looking at existing public address systems, flaws in them.
• Drawing inputs from personal problems/ views: Thinking of Uphaar theater tragedy (fire) and
experiencing difficulty in hearing from the last seats of convocation hall.
• Adding unique idea: Looking at including safety aspects into the design.
3.3 Conclusion
There were a few valuable lessons that I learnt from this analysis. Discussion with the designer made
me realize that the design problem should have been phrased more specifically giving clear indication
to the designer that a schematic level design is expected as the output. The current design question did
not set this context and hence even the structure of the design based on specifications, had to elicited
from the designer during the interview time. The mapping of certain design processes to categories put
forward by Cross et al. [7], underscored their importance in the design process.
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Chapter 4
Summary of seminar
The guiding question for this seminar was, 'What is Engineering design thinking?'.
I tried to answer this question by approaching Engineering design thinking from three perspectives. In
the first perspective of analysis of literature, I looked at what are the skills / competencies that
constitute design thinking as well as the most common design activities that designers take part in,
while going through the design process. I also examined the processes involved in learning design
thinking skills.
To fortify the notions that I developed from literature, I analyzed my own design process for detailed
design of a suitable problem. Mapping my design process to codes obtained from literature [] helped
me gain insights into the dynamics involved in design thinking. The third perspective was to analyze
design process of a second year PhD student in Electrical Engineering.
From the three approaches, I found that Engineering design thinking
• Is a systematic process.
• It involves a number of activities.
• It can be operationalized using competencies and sub-competencies.
• Detailed rubrics can be prepared to assess quality of design.
4.1 Additional design competencies
While most of the design thinking can be categorized using the five major competencies of structure
open problem, information gathering, multiple representations, convergent thinking and divergent
thinking, there are a few additional competencies that a designer must have.
A designer should be able to specify testing criteria / methodology. Writing test-benches along with
design is a major practice in programming and while designing electronic circuits using hardware
description languages.
A designer should have clear understanding of units, measurements and conversions between various
standards. For example, in public address system, the specification of microphones are given in very
many different ways. While some are in terms of voltage output and impedance, others are in terms of
sound pressure level and dBV or dBV/Pascal or mV/Pa, at some specific frequency. The disintegration
of Mars Climate Orbiter on September 23, 1999, due to calculation difference in metric Newtons and
pound force (lbf), underlines the importance of understanding and conversion among units. I did not
need to test my design nor did I use the SPL units in my design. However, my design is not complete in
all sense. For a complete design, such steps are important and therefore I think they must be coded in
the design thinking competency.
4.2 Competency to focus on
I also found from literature as well as my design analysis that divergent and convergent thinking in the
solution space is a powerful but often sparsely used competencies. I think that they merit more detailed
exploration as a design thinking skill and hence would like to explore them further.
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References
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thinking, teaching, and learning. Journal of Engineering Education, 94(1), 103-120.
2. Mehalik, M., & Schunn, C. (2007). What constitutes good design? A review of empirical studies of
design processes. International Journal of Engineering Education, 22(3), 519.
3. Mavinkurve, M. (2015). Development and Assessment of Engineering Design Competencies using a
Technology-Enhanced-Learning Environment. Submitted in partial fulfilment of the requirements of
the degree of Doctor of Philosophy, Inter-Disciplinary Program in Education Technology, IIT B. pg 26
4. Atman, C. J., Kilgore, D., & McKenna, A. F. (2008). Characterizing design learning through the use
of language: a mixed-methods study of engineering designers. Journal of Engineering Education, 97(3),
309-326.
5. Atman, C. J., Adams, R. S., Cardella, M. E., Turns, J., Mosborg, S., & Saleem, J. (2007).
Engineering design processes: A comparison of students and expert practitioners. Journal of
engineering education, 96(4), 359-379.
6. Cross, N. (2003). The expertise of exceptional designers. Expertise in Design, Creativity and
Cognition Press, University of Technology, Sydney, Australia, 23-35.
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